It is known to those skilled in the art that cumene can be oxidized to cumene hydroperoxide and that cumene hydroperoxide can be decomposed by various means to provide phenol and acetone.
In U.S. Pat. No. 2,889,368 to Hiratsuka there is a process discussed for the decomposition of various organic hydroperoxide substances, such as, for example, cumene hydroperoxide. The cumene hydroperoxide is decomposed in the presence of a 10 to 70% aqueous sulfuric acid solution at a temperature between about 50.degree. and 100.degree. C. to phenol and acetone, the yields amounting to 80-90%.
Today, the disadvantages of using soluble strong acid catalysts in this application include (a) the need for an efficient means of separating the phenol/acetone products from the acid or spent acid catalyst, (b) the need to neutralize said acids with caustic etc., (c) the disposal of salts generated as a result of said neutralization, and (d) the difficulty in obtaining &gt;99.9% purity phenol from such a process if there is any entrainment or contamination of the crude phenol/acetone product by said acid catalyst.
U.S. Pat. No. 2,715,145 concerns a process for increasing the yield of phenol by decomposing the material contained in the peroxide acidic catalyst decomposition mixture. Again it is disclosed that the decomposition can be promoted by the addition to the residue of acids such as sulphuric acid, phosphoric acid or sulphonic acids, as well as acid washed activated earth, such as fuller's earth.
A decomposition catalyst of sulfur dioxide or sulfuric acid is also used in U.S. Pat. No. 4,016,213 to obtain phenol and acetone from cumene hydroperoxide.
In U.S. Pat. No. 4,246,203 a hydroperoxide of an aromatic compound is converted to a volatile phenol and a carbonyl compound in a cleavage decomposition reaction. Here a wide range of both solid and liquid cleavage catalysts may be used including acetic acid, sulphur dioxide, sulphur, formic acid, phosphoric acid and fluoroboric acid, although sulfuric acid is preferred. Silica/alumina gave rather poor yields of phenol and acetone under these conditions.
Lewis acid catalysts were employed in the invention of U.S. Pat. No. 4,267,380, to Austin et al., to decompose cumene hydroperoxide to phenol and acetone. Some Lewis acids were unsatisfactory or, in some cases, found to be catalytically inert. Preferred Lewis acids were tungsten hexafluoride, silicon tetrafluoride, stannous chloride, stannic fluoride, antimony pentachloride, sulfur monochloride and sulfur tetrafluoride.
In U.S. Pat. No. 4,209,465, also to Austin et al., it was found that cumene hydroperoxide could be decomposed to phenol and acetone using an isolable carbonium, tropylium or oxonium salt, such as triphenylcarbonium tetrafluoroborate, as the catalyst.
In another patent to Austin et al., U.S. Pat. No. 4,267,379, cumene hydroperoxide is decomposed to phenol and acetone using boron trifluoride or boron trifluoride complexed with an oxygen-containing polar compound.
In U.S. Pat. No. 4,358,618 there is described a process for decomposing a cumene oxidation product mixture by mixing the product with an acid that lowers the cumene hydroperoxide concentration and converts most of the dimethylphenol carbinol to dicumyl peroxide.
In an article by Augustin et al, in Stud. Univ. Babes-Bolyai, Chem. 1986, 31, 19-23 (see Chem. Abstracts 107: 236170j, 1987), the life of synthetic aluminosilicate catalysts in the decomposition of cumene hydroperoxide was studied.
In U.S. Pat. No. 4,743,573 to Romano there was described catalysts for the selective decomposition of cumene hydroperoxide into phenol and acetone which comprise oxide forms of silicon, aluminum and boron in the form of crystals having a structure of zeolite wherein aluminum and boron replace silicon in the crystalline structure of silica and wherein the crystals are interconnected by oligomeric silica. The phenol selectivity is typically 80.5 to 96% with these catalyts in batch studies, and higher than 98% in continuous synthesis at cumene hydroperoxide conversion levels of 90%.
European patent application No. 203-632-A describes a catalyst for decomposition of cumene hydroperoxide to produce phenol and acetone comprising zeolite crystals containing boron and aluminum bonded with silica. A portion of the silicon atoms in the crystal lattice of silica are replaced by A1 and B and the zeolite crystals are bonded to each other by a siliceous bonding agent which allows the catalyst to assume the shape of mechanically stable microspheres.
Carboxylic acid derivatives have also been used to catalyze cumene hydroperoxide decomposition. See Izv. Akad. Nauk Turkm. 5512, Ser. Fiz.--Tekh, Khim, Geol. Nauk 1987, (2), 108-10 (Russ) and Chem. Abstracts 108: 55583w (1988).
Molybdenum, vanadium and titanium catalysts have also been used for the catalytic decomposition of cumyl hydroperoxide to yield mainly phenol and acetone. See Stozhkova, G. A., et al. (Yarosl. Politekh. Inst., Yaroslavl, USSR) Neftekhimiya 1987, 27(1), 137-41 (Russ) and Chem. Abstracts 107: 197676g (1987).
In an article titled "Catalysis: Selective Developments", Chem. Systems Report 84-3, 239-249, at Section 3.4320, the unusual properties of smectite clays which make them of interest as catalysts are discussed. These compositions are layered and exhibit a 2:1 relationship between tetrahedral and octahedral sites. In addition, the combination of cation exchange, intercalation and the fact that the distance between layers can be adjusted provide interesting possibilities.
There is a discussion of clay mineral catalysts, including "acid" montmorillonite clay catalysts in "Progress in Inorganic Chemistry", Vol. 35, p. 41 (1987). The process of pillaring this type of catalyst is discussed. Pillaring can convert a clay lamellar solid into a more heat resistant two dimensional zeolite material.
In the cases where acidic substances are utilized as the catalysts the yields are satisfactory, however many of these acid catalysts require substantial expenditure for production of phenol and acetone, there are disposal problems with spent acids or their salts, and there are difficulties in achieving &gt;99.9% purity phenol required by today's market place due to entrainment or breakthrough of said acids. In addition, by-products such as mesityl oxide, .alpha.-methylstyrene, acetophenone and 2-phenyl-2-propanol are produced along with the product and must somehow be removed and processed.
It would be a substantial advance in the art if phenol and acetone could be produced in yields approaching 100% by decomposition over an inexpensive heterogeneous catalyst using mild conditions. A catalyst which worked at very high space velocities using mild conditions and yet afforded high selectivities and yields with a smaller percentage of by-products would be particularly advantageous. Furthermore a very active, long life heterogeneous catalyst would also solve the catalyst disposal and acid entrainment problems cited above.